WASHINGTON – Final campaign finance tallies trickled out Thursday for a presidential race expected to be the most expensive in modern U.S. political history, showing last-minute contributions worth $33 million to political action committees backing Republican candidate Mitt Romney from a billionaire Las Vegas casino magnate and his wife who’ve been the election’s biggest money couple.

The late-campaign donations from Sheldon Adelson and his wife, Miriam – $23 million to the Karl Rove-backed American Crossroads and $10 million to the Restore Our Future “super” PAC – raised the couple’s total contributions for the 2012 election cycle to about $95 million, all for Republicans.

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Sheldon Adelson

The new campaign finance filings to the Federal Election Commission were among records covering the final few weeks of the race, when campaign organizations for Romney and President Barack Obama, along with a slew of super PACs, raised and spent millions toward an expected $2 billion campaign.

By late October, both campaigns already neared $1 billion in expenditures, and super PACs supporting Obama and Romney had spent more than $500 million in media ads. Politically oriented nonprofit “social welfare” organizations that do not have to declare their finances or identify their fundraisers have spent hundreds of millions more on so-called issue ads.

Adelson, who owns casinos in Las Vegas, Singapore and the Chinese territory of Macau, has been the top donor in the 2012 race. He has provided more than $54 million supporting Romney and other GOP presidential candidates and an additional $18 million for other Republicans.

The latest $33 million in donations from the Adelsons are detailed in campaign reports due to the FEC by midnight Thursday.

Adelson vowed early on in the presidential race that his political donations would top $100 million by the November election. His postelection super PAC total does not match that figure, but the casino magnate also hinted he would also give millions more to GOP-leaning nonprofits that do not have to report their war chests to the FEC but instead provide confidential figures to the Internal Revenue Service.

Along with his dominant presence in the presidential race, Adelson also poured money into super PACs backing several GOP Senate candidates in the final weeks of the election. More than $1.5 million in Adelson money went to a super PAC backing GOP candidate George Allen in Virginia, $1 million to a committee aiding Michigan candidate Peter Hoekstra and $500,000 to a super PAC supporting Sen. Scott Brown. All were defeated.

Other top last-minute donors to the pro-Romney Restore committee included Larry Ellison, head of software giant Oracle Corp., who gave $3 million, and Houston Texans owner Robert McNair, who gave $1 million. The Renco Group, a New York company headed by investor Ira Rennert, also gave $1 million.

Adelson recently told The Wall Street Journal that he would double his $100 investment in GOP causes by the next election and he has the financial muscle to do it. His massive campaign donations are backed by his lucrative casino holdings in the U.S. and Macau. The most recent November quarterly statement of his Las Vegas Sands Corp. estimated that Adelson’s casino revenues surged $1.11 billion in the first nine months of 2012 compared with the same period in 2011.

In late November, Adelson’s company announced a special dividend of $2.75 a share in anticipation of the threatened “fiscal cliff” rise in federal tax rates. The dividend move netted Adelson – who owns more than half of Sands’ 820 million shares – an estimated personal gain of as much as $1.2 billion, according to financial analysts.